Method of making metallized fibers



Dec. 2, 1958 v F. E. DRUMMOND METHOD OF MAKING METALLIZED FIBERS Filed Feb. 4. 1954 INVEIJVTOR. A rozsou E. onuuuoyo BY I (I I ATTORNEYS States Patent METHOD OF MAKING METALLIZED FIBERS Folsom E. Drummond, Washington, D. C., assignor to The Commonwealth Engineering Company of Ohio, Dayton, Ohio, a corporation of Ohio Application February 4, 1954,,Serial No. 408,176 1 Claim. '(Cl. 1s-s4 This invention relates to metallized filaments, fibers, andthe like, and more particularly to a method and apparatus for treatment of the same toproduce a metalllzed product. The invention is also adapted for producmg metallized fabrics or the like articles which are woven or felted from filaments which have been metalhzed in accordance with this invention.

Various methods and materials have been used heretofore in the treatment of fibers and fabrics to produce a product having a desirable characteristic property or comblnationof properties as desired. Many different liquid coating and impregnating compositions have been used to treat fibers and fabrics to coat and fill the same.

Puferentfibers and fabrics have also been coated using metal particles or pigments dispersed in liquid vehicles. woven therefrom has been achieved by immersion of the material in a bath of the composition and drying or curing to produce a finished product. In other instances the metal containing composition is applied by spraying so as to form a product having a metal-like surface or coating film. Such coating'films, however, are more in the nature of a sheath about the fibers or. fabric and tend to render the fiber or fabric stifi and unmanageable so that the finished product largely loses its textile characteristic properties.

.The present invention is designed to' overcome these disadvantages and to provide a metallized fiber, filament,

or fabric which has the characteristic properties of the metal used to treat the material, yet retains, at least to a large extent, its original characteristic textile orfiberlike'properties.

Although the invention will be described as applied primarily to a fiber or filament, it is intended that the invention will include like treatment of fabrics or articles woven or felted, or. otherwise fabricated which are made from various type fibers or filaments. Theainven'tion accordingly contemplates the treatment of one or more fibers or'filaments to produce a metallized fiber product.

Application of such coatings to fibers and fabric accordance with this invention, preferably during the spinning of the filament or fabrication of the fibrous product into a thread or fiber to produce a product wherein the fibers are individual filaments containing uniform dispersions of metal particles.

In the case of wet spinning, tion of a high molecular weightfilm and fiber-forming material is wet spun into a coagulating solution from a spinneret and the resultant fiber taken up on a Godet wheel and thence onto a windup bobbinor spool, the fiber before passing to the windup bobbin or spool, and preferably while being taken up on the Godet Wheel is.

subjected to gaseous metaldecomposition treatment to thus impregnate and coat the filaments with the desired metal.

In dry spinning of fibers or filaments, as by forcing a solution of a resin or film-forming material dissolved in solvent through a suitable die into a heated gaseous medium which removes the solvent and precipitates the resin so that it can be drawn out into a continuous length I thread or filament, the fiber is subjected to gaseous metal treatment during or immediately after the removal of the solvent to produce the metallized fiber. The gaseous metal treatment is suitably combined with the solvent Q removal operation whereby the solvent is removed and concurrently replaced with metal by decomposition of the gaseous metal compound which is brought into in: timate contact with the fiber and heat decomposed.

Where the solvent ,vapor mixture tends to interfere with the gaseousmetal treatment the operation is modified to provide for removal of the solvent before the fibers are subjected to the gaseous metal deposition.

In the production of fibers by the application of heat and extrusion, the fiber is extruded from the die into a chamber in which there is circulated a heat ,decomposable gaseousmetal compound 'or gaseous mixture con taining the same to elfect the metallizationof the fiber while 'it is still in a heated and semiplastic condition.

In this manner the heatrequired for softening and extruding the resin or thermoplastic material through the In accordance with the broad concept of theinvention, fibers of different type or mixture of such fibers individually or collectively, are treated with a heat-decomposable gaseous metal compound or mixture thereof to produce the desired metallized fiber product. In each instance the gaseous metal compound employed and the conditions of treatment may be varied, depending upon the desired metallized fiber, product andthe nature of,

the fiber being treated. V 7

.Various fibers may be treated in accordance with 'this invention, such as vegetable fibers, e. g., cotton, hemp, jute, etc.; animal fibers, e. g., silk, wool, and animal hair or fur and the like which may be classified as essentially proteins; inorganic fibers, e. g., asbestos; semisynthetic fibers, e; g., rayons which are made from cellulose or its derivatives, such as cotton linters,.wood pulp, etc.; manufactured protein fibers, e. g., casein and vegetableproteiiis extracted'from various plants; inorganic fibers, egg, glass..,fiber,-, spun glass, etc.;andjsynthetic.

die is used to assist the gaseous metal de composition and .metallization operation.

'-'used, for example, gaseous metal carbonyls, metal hyv drides, metal alkyls,,metal halides, and also nitroxyl compounds, nitrosyl carbonyls, and the like. Metal compounds of the carbonyl type which are useful arecarbonyls of'nickel, iron, chromium, molybdenum, cobalt,

and mixed carbonyls,

Illustrative compounds of other groups are the nitroxyls, such as copper nitroxyl; nitrosyl carbonyls, for

example, cobalt nitrosyl carbonyl; hydrides, such as antimony hydride, tin hydride; metal alkyls, such as chromyl chloride; and carbonyl halogens,'for example," osmium carbonyl bromide, ruthenium carbonyl chlorlde, i

and the like. I

The compounds each have a dilferent temperature of decomposition. The decomposition, however, generally takes place slowly at lower temperature and increases as the-temperature is raised through a particular range. For example, nickel carbonyl starts to decompose slowly at about F. and thereafter decomposition'continues during the time of heating upward to 375 .F. to 380 F;

Many of the metal carbonyls and hydrides may be ef- Patented Dec. 2, 1958 for example ,where a. solufectively and efilciently decomposed at a temperature and range of 300 Fl to 450 F. The gaseous metal compound used in each instancegtdepends upon the melting point of-.t he. fiber being treated and the metal desired to bedeposited.onthe-fibersl Generally the working tern; perature, usingmetal carbonyls, lies in .the rangeof about 300?: F. to 425 F.- Where the fiber has a relatively low.melting .point or plasticity, the lower decomposing temperature compounds are. utilized.

-In carryingout the gaseous metal decomposition in accordance-with the invention, the gaseous metal compound is directed into'a chamber wherein it is heated to its decompositions temperature and brought in contact with the fiber.,- The .fiber or filament is preferably.continuously moved through the gaseous depositionzchamber and the amountof metaldeposited inthe fiber is controlled by regulatingthe time in which the fiber is subjected to the gaseous platingoperat-ion.

The i nvention-willlbe more particularly described with respect to dryspinning and .pla sticextrusion methods of producingtheyfihers, but it will be understood that the invention is adapted also for vwet spinning as. aforementioned.

The accompanying drawing .illustrates one embodiment.

of the apparatus and 'mode of operation for forming metallized fibers in accordance Withthis invention.

[Figurel is a diagrammatic illustrationof an apparatus for metallizing dry spun fibers, the-apparatus being shown in vertical cross-section;

Figurel is a similarvertical cross-sectional view of an apparatus illustrated diagrammatically for extruding fibers and metallizingthe same simultaneously; and

Figure 3 illustrates diagrammatically a modification of a dryspinning process wherein the gaseous metal deposition iscarried outsitnultaneou'sly withremoval of the solvenh,

In the" preparation .of films, fibers, rods, and other shapes, by. the .dry spinningprocess, the solution of resin-or the like. high molecular weight fiber-forming material is forced through, asuitable. die into-a gaseous medium which removes. theqSOlVfiIlt and precipitates the resin as. a continuous-thread or fiber. Utilizingsuch a dry spinning. operation, the apparatusas diagrammatically illustratedin-Figure--l, may be used to.carry out both the ,dry, spinning: operation .and. the -metallization in accordancetwith this-invention.

Referringto Figure-l of thedrawing, there is illustrated a vertically, disposed apparatus 5 having a plurality. of chambers 6,-7, and 8. The: apparatus is arranged to receive a conduit 1-0 at the top of the chamber 6 for intro-.

ducingt the film-forming fiber in solution. The film-forming solution is conducted to a spinneret Hand is delivered therefrom-in the form of fine filaments 12 which are :twisted and drawn downwardly through the chambers 6, 7, and '8 and passed outwardly therefrom over the rolls 16;

In the'apparatusillustrated, heated air is circulated into thegchamber 6 through'the conduit openin 18 and is passed upwardly through-the funnel-shaped'bafiie 19 so as to direct the heated air against the fibers as drawn from the-spinneret- Discharge of the hot air'and solvent which has-beenevaporated from the'filaments 12 to precipitate theifiber is conducted outward through theexit 20 and tosolvent recovery means. The fiber 14 thus formed is passed downwardly into the chamber 7 which is arranged, to be heated by'the heating coils- 22 which may suitably be steam coils. This chamber is provided with heated insulated walls 24: and heat decomposable gaseous metalis admitted and-circulatedthrough this chamber through the conduit opening. 26.. and outwardly through; the-exit 27. The length 0f thechamber 7 is such as will provide: sufiicient' time for the thread, during passage therethrough, to deposit the-desired amount of metal in l and on the fiber.

The; fiberis drawn thrOugh the chamber 7 through the port openings 29 and 30, which ports are maintained substantially' sealed against the exit of gaseous metal compound by means of the soft, spongy packing 32 and 33 of the ports 29 and 30 respectively. After passmg through the chamber 7, the fiber is drawn downwardly through the air cooling chamber 8. Air for cooling the fiber is admitted to the chamber 8 through a conduit 35 and after passing around the bafiles 37 arranged in the chamber as indicated by the arrows, the air is conducted out through the exit 40; The cooled and metallized fiber 41 is then withdrawn from the cooling chamber through the port 42 and passed by the roll 16 to the next operation.

In Figure 2 there is shown diagrammatically an apparatus for heat extruding fiber and metallizing the same simultaneously. As illustrated, the apparatus comprises a heated extrusion chamber 50 in which the material to be extruded, for example as shown at 52, and which is pref'erablyin powdered form; is compressed by a piston 54 while the'resin or thermoplastic material is heated by the heating coils 55. The ext'rusion apparatus comprises a die 58 which is providedwith port openings 59 for re ceiving the plastic material in molten condition, whereby the same is extruded through the die opening- 60 in-the form of a filament or thread 61 into the chamber 64. This chamber is provided with port openings 66 and 67 through which'is admitted and circulated about the fiber a heat decomposable gaseous metal compound. The

chamber 64 is heated by means of heating coils 70 which are arranged in the walls thereof, and the temperature maintained high enough to cause decomposition of the heat decomposable gaseous metal compound admitted into the chamber. In this manner the hot fiber'61 which is extruded from the die 58 is metallized-by gaseous metal deposition'in its passage through this chamber. After the metallizing treatment the fiber is drawn"outwardlythroughthe port72 into'the air cooling chamber 74. Air for cooling the fiber is admittedthrough. the port 76' and circulated about the baffles 77 and :outwardly through theiexit 78. The finished metallized fiber-79 is withdrawn by the rolls 80 through the port 81' passed to the next operation.

The apparatus shown in 'Figure-3 is ,a modification "of the apparatus of Figure l for carryingout dry-spinning and metallizing the fibers in accordance with'thisinvention. Utilizing the apparatus as shown'inFigure 3, ar-- rangement is made fortreatingithe thread' so astocon currently remove the volatile solvent and perform the gaseous deposition of the metal on the thread.- Whilethe same'is being spun. I

In theembodimentshownin'Figure3, the' solution of' fiber-formingv material is admitted-through a conduit 86 at the top lot the enclosure 87, the enclosure-87 being provided with insulating walls- 88 and providing an elongated chamber-90. The'material is delivered to the spinneret 91"and-'the filaments 92 are drawn out and twisted to form the fiber93' which is drawndownwardly through the chamber and outwardly through. the exit port 95' The. thread 93, after being subjected to the metallization is drawn into the aircooling. chamber 100, is drawnoutwardly through the porta105, and the-finished metallized fiber 106 is drawn between the rolls 107. The rolls 107 are preferably arranged to be driven at'a uniform speedso as to withdraw "the fiber'andpass it along to thenext operation.

Suitable bafiies 110 are providedinthe air-.chambe'r to guide the air or cooling gases 'therethrlough and in contact with the fiber drawn therethrough. The/ports 111 and 112 are provided in the air chamber 100 for admitting cooling gases such as air or inert gas therethrough, as indicated by the arrows. r I The embodiment shown in Figure 3 isutilized when the solvent in the fiber-forming material does not'interfere with the operation of the gaseous metal deposition' so that the heated gases passing through the elongatedchamber 90 function to both remove the solvent and precipitate the fiber-forming material, as well as deposit the metal constituent on the filaments forming the fiber as the fiber is being formed and drawn along through the apparatus.

The apparatus and metallizing method for treating fibers as described and illustrated in the drawing is especially useful in the preparation of synthetic fibers and semi-synthetic fibers, and such as are produced by wet or dry spinning, or heat extruded to form a thread or fiber.

For example, the invention is useful in the production of fibers of acrylonitrile polymers, such as polyacrylonitrile and comprising copolymers of over 80% acrylonitrile and up to 20% of other copolymerizable olefinic monomers, e. g., vinyl acetate, vinyl pyridine, methacrylonitrile, vinylidene chloride, and esters of acrylic and methacrylic acids. In the preparation of this type of fibers by dry spinning, the practice generally involves the volatilization of high boiling solvents such as N,N-dimethylformamide, ethylene carbonate, N,N-dimethylacetamide and butyrolacetone, and the like, as used to form a solution of the fiber-forming resin. These solvents often cause discoloration of the fiber unless the temperature is carefully controlled.

The process of the present invention permits controlled heating and removal of the solvent to be effected during or immediately following the spinning operation and allows for metallization of the fiber without subjecting the fiber to prolonged high temperatures which is to be avoided. The hot gases, even during gaseous metal deposition are preferably exposed to the fiber for a time just sutficient to remove the solvent and deposit the metal. For example, in the preferred practice, the metallization operation is completed in a few seconds, and preferably less than a minute, depending of course, on the amount of metal to be applied to the fiber. The metallization preferably is carried out at the same time of the spinning and removal of the solvent to produce the fiber. In the case of extruded fi-ber, the heat of the fiber as it is extruded from the die is used to assist in the carrying out of the gaseous metal deposition to produce a metallized fiber. This is an economical advantage.

While the process is adapted for continuous operation, e. g., the continuous drawing of the fiber from the spinning and extrusion unit at a substantially uniform speed, the process and apparatus are readily adapted for discontinuous operation if desired.

In the preferred practice of carrying out the process, the fiber as it comes from the spinneret or extrusion die and while heated to a temperature between 250 F. and 450 F., depending upon the fiber being formed, the filaments or strands making up the thread or continuous length fiber are concurrently subjected to a decomposable gaseous metal compound. Employing, for example, nickel carbonyl which decomposes in this temperature range, metallic nickel particles are deposited on and in the filaments. A metallized nickel fiber or thread is thus produced. Similarly other metal carbonyls, hydrides or the like heat decomposable metal compounds as afore-' mentioned may be used to produce a particular metallized fiber.

In utilizing the apparatus and method of metallizing fiber in accordance with this invention, filaments, strands, and shapes made of polymers of polypyrrolidone, which is a thermoplastic resin having a melting point of 480 F. to 500 F. are readily metallized. The filaments or fibers are then useful in making textile products having a metallized finish. These synthetic resin fibers are spun by cold drawing in a conventional manner.

Other suitable fibers having a relatively high melting ."point are the tetrafluorethylene polymer compositions containing polyorgano-siloxane and alpha-amino acid polyamides, such as produced by copolymerizing N- carboanhydrides of alpha-aminocarboxylic acids. Such synthetic resins have a melting point of 335 F. to 350 F. Similar high molecular weight polyunsaturated compounds which include the various natural rubbers and resins, for example as described in U. S. Patent 2,654,680, may be metallized in accordance with this invention.

Polymers of hydroxy polypeptic acid which have a melting point of 450 F. are readily metallized. Also epoxy alkoxy resins polymerized by subjecting the same to epoxide coupling reaction in the presence of a catalyst and drawn into fine filaments may be metallized in accordance with this invention.

The gaseous metal compound used in each instance will depend upon the melting point of the fiber being metallized and methods of fabrication.

It will be understood that while the invention is described with particular reference to dry spinning and extrusion methods for forming the fiber, the apparatus and method is readily adapted for treating wet spun, felted or otherwise built-up fibers or filaments and which may or may not be woven or felted together.

The invention is intended to include various methods of forming the fiber and in which the fiber is drawn through a gaseous metal plating chamber and subjected to gaseous plating to produce the finished metallized fiber.

In the process a stream of hot gaseous metal is brought into direct contact with the heated fiber at temperatures which bring about decomposition of the gaseous metal compound to cause deposition of the metal in very fine particles on and into the interstices of the fiber or filament. The gaseous atmosphere may be formed by mixing inert'gas with the vapors of a volatile metal compound or by atomizing a liquid metal compound into a blast of hot inert gas such as carbon dioxide, nitrogen, helium or the like. Such inert gases may be used as a carrier medium for the gaseous metal compound. Hydrogen may also be used as well as oxygen so long as the gas does not have any deleterious effect on the fiber being metallized.

In place of using air for cooling the fibers after the metallizing operation, inert gases, such as carbon dioxide, may be used for this purpose. Also mixtures of air with other diluting gases may be employed if desired as a cooling medium. 7

It will be further understood that the proportion of materials and details of operation, and conditions, may be modified according to the particular fiber being treated and the gaseous metal compound used without departing from the spirit and scope of this invention as more particularly defined in the appended claim.

What is claimed is:

A method of coating freshly extruded organic fibers with metal which comprises extruding a fiber as a filament of continuous length from a fiber-forming substance dissolved in volatile organic solvent, heating said fiber thus formed and which contains solvent to a temperature whereby substantially all of the volatile solvent is driven ofi, and thereafter subjecting said fiber to a temperature between 250 F. and 450 F. in an atmosphere containing a heat-decomposable gaseous metal compound, heating said heat-decomposable gaseous metal compound while in contact with said fiber to cause thermal decomposition of said gaseous metal compound and deposition of said metal constituent onto the fiber, the fiber being metal coated by gaseous metal deposition immediately after the solvent is removed, said metal compound being selected from the carbonyls of metal, and carbonyls of nicke1,- iron,- chromium, molybdenum, cobalt, tin, andmixed carbonyls thereofl- Refere'nces Cited th'file of this patent UNITED STATES PATENTS 8* Godley July 31, 1951' Da'v'is et al:" June--10,"-1952 Brennan; Nov. 4,1952 Hammond'ffefi'al; Apr: 28,1953 Tdulmin" Nov; 3, 1953 Schladitz" Jan. 4, 1955 Nachtm'an Ian. 11, 1955' Pa'wlyk' Feb. 15, 1955' 

